> ## Documentation Index
> Fetch the complete documentation index at: https://docs.apimart.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# SkyReels V4 Video Generation

>  - Two model tiers: Fast (speed-optimized) and Std (quality-optimized)
- Three modes auto-routed by request fields: Text-to-Video (T2V), Image-to-Video (I2V), Multimodal Reference (Omni)
- 480p / 720p / 1080p resolution, 3 ~ 15 seconds duration
- Advanced features: first/end/key frame, reference images, reference videos, grid collage, video extension, audio sync
- Async processing mode, returns a task ID for later query 

<RequestExample>
  ```bash cURL theme={null}
  curl --request POST \
    --url https://api.apimart.ai/v1/videos/generations \
    --header 'Authorization: Bearer <token>' \
    --header 'Content-Type: application/json' \
    --data '{
      "model": "skyreels-v4-fast",
      "prompt": "A serene forest at sunset with golden light filtering through the trees.",
      "duration": 5,
      "resolution": "1080p",
      "aspect_ratio": "16:9",
      "prompt_optimizer": true
    }'
  ```

  ```python Python theme={null}
  import requests

  url = "https://api.apimart.ai/v1/videos/generations"

  payload = {
      "model": "skyreels-v4-fast",
      "prompt": "A serene forest at sunset with golden light filtering through the trees.",
      "duration": 5,
      "resolution": "1080p",
      "aspect_ratio": "16:9",
      "prompt_optimizer": True
  }

  headers = {
      "Authorization": "Bearer <token>",
      "Content-Type": "application/json"
  }

  response = requests.post(url, json=payload, headers=headers)

  print(response.json())
  ```

  ```javascript JavaScript theme={null}
  const url = "https://api.apimart.ai/v1/videos/generations";

  const payload = {
    model: "skyreels-v4-fast",
    prompt: "A serene forest at sunset with golden light filtering through the trees.",
    duration: 5,
    resolution: "1080p",
    aspect_ratio: "16:9",
    prompt_optimizer: true
  };

  const headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
  };

  fetch(url, {
    method: "POST",
    headers: headers,
    body: JSON.stringify(payload)
  })
    .then(response => response.json())
    .then(data => console.log(data))
    .catch(error => console.error('Error:', error));
  ```

  ```go Go theme={null}
  package main

  import (
      "bytes"
      "encoding/json"
      "fmt"
      "io/ioutil"
      "net/http"
  )

  func main() {
      url := "https://api.apimart.ai/v1/videos/generations"

      payload := map[string]interface{}{
          "model":            "skyreels-v4-fast",
          "prompt":           "A serene forest at sunset with golden light filtering through the trees.",
          "duration":         5,
          "resolution":       "1080p",
          "aspect_ratio":     "16:9",
          "prompt_optimizer": true,
      }

      jsonData, _ := json.Marshal(payload)

      req, _ := http.NewRequest("POST", url, bytes.NewBuffer(jsonData))
      req.Header.Set("Authorization", "Bearer <token>")
      req.Header.Set("Content-Type", "application/json")

      client := &http.Client{}
      resp, err := client.Do(req)
      if err != nil {
          panic(err)
      }
      defer resp.Body.Close()

      body, _ := ioutil.ReadAll(resp.Body)
      fmt.Println(string(body))
  }
  ```

  ```java Java theme={null}
  import java.net.http.HttpClient;
  import java.net.http.HttpRequest;
  import java.net.http.HttpResponse;
  import java.net.URI;

  public class Main {
      public static void main(String[] args) throws Exception {
          String url = "https://api.apimart.ai/v1/videos/generations";

          String payload = """
          {
            "model": "skyreels-v4-fast",
            "prompt": "A serene forest at sunset with golden light filtering through the trees.",
            "duration": 5,
            "resolution": "1080p",
            "aspect_ratio": "16:9",
            "prompt_optimizer": true
          }
          """;

          HttpClient client = HttpClient.newHttpClient();
          HttpRequest request = HttpRequest.newBuilder()
              .uri(URI.create(url))
              .header("Authorization", "Bearer <token>")
              .header("Content-Type", "application/json")
              .POST(HttpRequest.BodyPublishers.ofString(payload))
              .build();

          HttpResponse<String> response = client.send(request,
              HttpResponse.BodyHandlers.ofString());

          System.out.println(response.body());
      }
  }
  ```

  ```php PHP theme={null}
  <?php

  $url = "https://api.apimart.ai/v1/videos/generations";

  $payload = [
      "model" => "skyreels-v4-fast",
      "prompt" => "A serene forest at sunset with golden light filtering through the trees.",
      "duration" => 5,
      "resolution" => "1080p",
      "aspect_ratio" => "16:9",
      "prompt_optimizer" => true
  ];

  $ch = curl_init($url);
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
  curl_setopt($ch, CURLOPT_POST, true);
  curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($payload));
  curl_setopt($ch, CURLOPT_HTTPHEADER, [
      "Authorization: Bearer <token>",
      "Content-Type: application/json"
  ]);

  $response = curl_exec($ch);
  curl_close($ch);

  echo $response;
  ?>
  ```

  ```ruby Ruby theme={null}
  require 'net/http'
  require 'json'
  require 'uri'

  url = URI("https://api.apimart.ai/v1/videos/generations")

  payload = {
    model: "skyreels-v4-fast",
    prompt: "A serene forest at sunset with golden light filtering through the trees.",
    duration: 5,
    resolution: "1080p",
    aspect_ratio: "16:9",
    prompt_optimizer: true
  }

  http = Net::HTTP.new(url.host, url.port)
  http.use_ssl = true

  request = Net::HTTP::Post.new(url)
  request["Authorization"] = "Bearer <token>"
  request["Content-Type"] = "application/json"
  request.body = payload.to_json

  response = http.request(request)
  puts response.body
  ```

  ```swift Swift theme={null}
  import Foundation

  let url = URL(string: "https://api.apimart.ai/v1/videos/generations")!

  let payload: [String: Any] = [
      "model": "skyreels-v4-fast",
      "prompt": "A serene forest at sunset with golden light filtering through the trees.",
      "duration": 5,
      "resolution": "1080p",
      "aspect_ratio": "16:9",
      "prompt_optimizer": true
  ]

  var request = URLRequest(url: url)
  request.httpMethod = "POST"
  request.setValue("Bearer <token>", forHTTPHeaderField: "Authorization")
  request.setValue("application/json", forHTTPHeaderField: "Content-Type")
  request.httpBody = try? JSONSerialization.data(withJSONObject: payload)

  let task = URLSession.shared.dataTask(with: request) { data, response, error in
      if let error = error {
          print("Error: \(error)")
          return
      }

      if let data = data, let responseString = String(data: data, encoding: .utf8) {
          print(responseString)
      }
  }

  task.resume()
  ```

  ```csharp C# theme={null}
  using System;
  using System.Net.Http;
  using System.Text;
  using System.Threading.Tasks;

  class Program
  {
      static async Task Main(string[] args)
      {
          var url = "https://api.apimart.ai/v1/videos/generations";

          var payload = @"{
              ""model"": ""skyreels-v4-fast"",
              ""prompt"": ""A serene forest at sunset with golden light filtering through the trees."",
              ""duration"": 5,
              ""resolution"": ""1080p"",
              ""aspect_ratio"": ""16:9"",
              ""prompt_optimizer"": true
          }";

          using var client = new HttpClient();
          client.DefaultRequestHeaders.Add("Authorization", "Bearer <token>");

          var content = new StringContent(payload, Encoding.UTF8, "application/json");
          var response = await client.PostAsync(url, content);
          var result = await response.Content.ReadAsStringAsync();

          Console.WriteLine(result);
      }
  }
  ```
</RequestExample>

<ResponseExample>
  ```json 200 theme={null}
  {
    "code": 200,
    "data": [
      {
        "status": "submitted",
        "task_id": "task_01KPEY5H3NQ2W8D7T6VB3F9GR4"
      }
    ]
  }
  ```

  ```json 400 theme={null}
  {
    "error": {
      "code": 400,
      "message": "Invalid request parameters",
      "type": "invalid_request_error"
    }
  }
  ```

  ```json 401 theme={null}
  {
    "error": {
      "code": 401,
      "message": "Authentication failed, please check your API key",
      "type": "authentication_error"
    }
  }
  ```

  ```json 402 theme={null}
  {
    "error": {
      "code": 402,
      "message": "Insufficient account balance, please top up and try again",
      "type": "payment_required"
    }
  }
  ```

  ```json 422 theme={null}
  {
    "error": {
      "code": 422,
      "message": "Parameter conflict or invalid value (e.g. I2V and Omni fields passed simultaneously)",
      "type": "invalid_request_error"
    }
  }
  ```

  ```json 429 theme={null}
  {
    "error": {
      "code": 429,
      "message": "Too many requests, please try again later",
      "type": "rate_limit_error"
    }
  }
  ```

  ```json 500 theme={null}
  {
    "error": {
      "code": 500,
      "message": "Internal server error, please retry later",
      "type": "server_error"
    }
  }
  ```
</ResponseExample>

## Authorization

<ParamField header="Authorization" type="string" required>
  All API endpoints require Bearer Token authentication

  Get your API Key:

  Visit the [API Key Management Page](https://apimart.ai/keys) to get your API Key

  Add to the request header:

  ```
  Authorization: Bearer YOUR_API_KEY
  ```
</ParamField>

## Generation Modes

SkyReels V4 auto-routes to the correct mode based on request fields — **no `mode` field needed**:

| Mode                            | Trigger                                                             | Capability                                                                     |
| ------------------------------- | ------------------------------------------------------------------- | ------------------------------------------------------------------------------ |
| **T2V** (Text-to-Video)         | Only `prompt` + general fields                                      | Pure text-driven generation                                                    |
| **I2V** (Image-to-Video)        | Any of `first_frame_image` / `end_frame_image` / `mid_frame_images` | First/end/key frame control                                                    |
| **Omni** (Multimodal Reference) | Any of `ref_images` / `ref_videos`                                  | Subject reference, grid collage, motion reference, video extension, audio sync |

<Warning>
  **Strict mutual exclusion**: I2V fields (`first_frame_image` / `end_frame_image` / `mid_frame_images`) and Omni fields (`ref_images` / `ref_videos`) cannot be used together, otherwise returns 422.
</Warning>

<Note>
  **`@tag` mechanism**: When using `mid_frame_images` / `ref_images` / `ref_videos`, each element must declare a `tag` starting with `@` (e.g., `@image1`, `@Actor-1`, `@video1`), and the `tag` **must appear in the `prompt`**.

  Think of `prompt` as the "script" and `tag` as a "character pointer" to specific assets (images / videos). For example, a prompt like `"@Actor-1 walks into the scene of @video1"` instructs the system to inject the reference image subject tied to `@Actor-1` and the motion reference tied to `@video1` into the generation process.
</Note>

## Request Parameters

### General Fields

<ParamField body="model" type="string" required>
  Two model tiers are available:

  | Model              | Positioning                                    | Use Cases                                            |
  | ------------------ | ---------------------------------------------- | ---------------------------------------------------- |
  | `skyreels-v4-fast` | Speed-first                                    | Quick previews, batch generation, daily content      |
  | `skyreels-v4-std`  | Quality-first (25\~30% higher price than Fast) | Key shots, high-detail requirements, formal delivery |

  <Warning>
    **The `model` field must be explicitly provided — no default value.**
  </Warning>

  <Tip>
    **Pricing is strongly tied to resolution and whether `ref_videos` is used**: 1080p is significantly more expensive than 480p / 720p; tiers with `ref_videos` (video input) cost \~1.5 \~ 2× compared to those without. Simultaneous audio and video output is not yet supported.
  </Tip>
</ParamField>

<ParamField body="prompt" type="string" required>
  Text prompt, max **1280 tokens**

  Describe scenes, subjects, actions, styles in detail for better generation results.

  When using `ref_images` / `ref_videos` / `mid_frame_images`, the `prompt` **must contain** the corresponding `@tag` (e.g., `@Actor-1`, `@video1`, `@image1`).

  Example: `"@Actor-1 walks through a neon-lit street at night."`
</ParamField>

<ParamField body="duration" type="integer" default="5">
  Output video duration (seconds)

  * Range: `[3, 15]`
  * Default: `5`

  <Warning>
    When `ref_videos.type=reference` is provided, `duration` is overridden by the reference video length (max 10 seconds).
  </Warning>
</ParamField>

<ParamField body="resolution" type="string" default="1080p">
  Video resolution

  Options:

  * `480p`
  * `720p`
  * `1080p` (default)
</ParamField>

<ParamField body="aspect_ratio" type="string" default="16:9">
  Aspect ratio

  Options:

  * `16:9` (default)
  * `4:3`
  * `1:1`
  * `9:16`
  * `3:4`

  <Warning>
    **`aspect_ratio` is ignored in I2V mode** (output ratio is determined by the input image); also ignored when Omni is combined with `ref_videos`.
  </Warning>
</ParamField>

<ParamField body="prompt_optimizer" type="boolean" default="true">
  Whether to auto-optimize the prompt

  When enabled, the system automatically optimizes your prompt for better generation results.
</ParamField>

### I2V-Specific Fields

<ParamField body="first_frame_image" type="string">
  First frame image URL (jpg / jpeg / png / gif / bmp)

  When provided, this image is used as the **starting frame** of the video.
</ParamField>

<ParamField body="end_frame_image" type="string">
  End frame image URL (jpg / jpeg / png / gif / bmp)

  When provided, this image is used as the **ending frame** of the video. Can be combined with `first_frame_image` for first-and-last-frame control.
</ParamField>

<ParamField body="mid_frame_images" type="object[]">
  Mid keyframe list, **up to 6**. Each element has the following structure:

  <Expandable title="mid_frame_images element">
    <ResponseField name="tag" type="string" required>
      Must start with `@` and appear in the `prompt`, e.g., `@image1`
    </ResponseField>

    <ResponseField name="image_url" type="string" required>
      Image URL (jpg / jpeg / png / gif / bmp)
    </ResponseField>

    <ResponseField name="time_stamp" type="integer" default="-1">
      Timestamp of appearance (seconds). Default `-1` (unspecified); when specified, must satisfy `0 < time_stamp < duration`.
    </ResponseField>
  </Expandable>
</ParamField>

### Omni-Specific Fields

<ParamField body="ref_images" type="object[]">
  Reference image list (all elements must share the same `type`). Each element has the following structure:

  <Expandable title="ref_images element">
    <ResponseField name="tag" type="string" required>
      Must start with `@` and appear in the `prompt`, e.g., `@Actor-1`
    </ResponseField>

    <ResponseField name="type" type="string" required>
      Reference type:

      * `image` - Regular reference image (list length 1~~3; each `image_urls` length 1~~5)
      * `grid` - Grid collage, i.e., a single image composed of multiple tiles (e.g., 2×2, 3×3); list length must = 1, `image_urls` must be 1 image
    </ResponseField>

    <ResponseField name="image_urls" type="string[]" required>
      Array of image URLs
    </ResponseField>

    <ResponseField name="audio_url" type="string">
      Voice audio URL (**only supported when `type=image`**, audio duration ≤ 15 seconds)
    </ResponseField>
  </Expandable>
</ParamField>

<ParamField body="ref_videos" type="object[]">
  Reference video list, **up to 1**. Each element has the following structure:

  <Expandable title="ref_videos element">
    <ResponseField name="tag" type="string" required>
      Must start with `@` and appear in the `prompt`, e.g., `@video1`
    </ResponseField>

    <ResponseField name="type" type="string" required>
      Reference type:

      * `reference` - Motion / subject reference, **overrides `duration`** (follows the reference video length, max 10 seconds), carries input video audio by default; **can be combined with `ref_images.type=image`**
      * `extend` - Video extension, billed by the requested `duration`; **cannot be combined with `ref_images`**
    </ResponseField>

    <ResponseField name="video_url" type="string" required>
      Video URL (MP4 / MOV, duration ≤ 15 seconds)
    </ResponseField>
  </Expandable>
</ParamField>

## Supported Scenarios

The following scenarios are **supported by both** `skyreels-v4-fast` and `skyreels-v4-std`:

| Scenario                     | Mode | Required Fields                           | Typical Use Case                                             |
| ---------------------------- | ---- | ----------------------------------------- | ------------------------------------------------------------ |
| Text-to-Video                | T2V  | `prompt`                                  | Pure text-driven, rapid concept shots                        |
| Image-to-Video - First Frame | I2V  | `first_frame_image`                       | Still-to-video with a specified starting frame               |
| Image-to-Video - End Frame   | I2V  | `end_frame_image`                         | Specifies the closing frame                                  |
| Image-to-Video - Keyframes   | I2V  | `mid_frame_images` (1 \~ 6)               | First + end + mid keyframes for precise pacing               |
| Omni Single/Multi-Subject    | Omni | `ref_images` (`type=image`)               | Character consistency, multi-subject framing                 |
| Omni Grid Collage            | Omni | `ref_images` (`type=grid`, 1 image)       | Step-by-step process videos (tutorials, recipes, demos)      |
| Omni Motion Reference        | Omni | `ref_videos` (`type=reference`)           | Replicate the motion, subject, or style of a reference video |
| Omni Video Extension         | Omni | `ref_videos` (`type=extend`)              | Continue an existing video with new content                  |
| Omni Audio Sync              | Omni | `ref_images` (`type=image`) + `audio_url` | Digital human narration, audio-driven lip-sync               |

## Parameter Constraints

Violating any of the following will cause the request to be rejected with a **422** response, **no billing occurs**:

| Parameter                   | Constraint                                                                                                               |
| --------------------------- | ------------------------------------------------------------------------------------------------------------------------ |
| `prompt`                    | Max 1280 tokens                                                                                                          |
| `duration`                  | `[3, 15]` seconds; overridden by reference video length (max 10s) when `ref_videos.type=reference`                       |
| `resolution`                | Only `480p` / `720p` / `1080p`                                                                                           |
| `aspect_ratio`              | `16:9` / `4:3` / `1:1` / `9:16` / `3:4`; ignored in I2V; ignored when Omni carries `ref_videos`                          |
| `mid_frame_images`          | Up to 6; `time_stamp` must be `-1` or within `(0, duration)`                                                             |
| `ref_images` overall        | All elements must share the same `type`; cannot coexist with I2V fields                                                  |
| `ref_images.type=grid`      | List length must = 1; `image_urls` must be 1 image                                                                       |
| `ref_images.type=image`     | List length 1 \~ 3; each `image_urls` length 1 \~ 5                                                                      |
| `ref_images.audio_url`      | Only supported when `type=image`, audio ≤ 15 seconds                                                                     |
| `ref_videos`                | Up to 1; `video_url` MP4 / MOV, ≤ 15 seconds                                                                             |
| `ref_videos.type=reference` | Overrides requested `duration` (max 10s), can combine with `ref_images.type=image`, carries input video audio by default |
| `ref_videos.type=extend`    | Billed by requested `duration`; **cannot combine with `ref_images`**                                                     |
| `tag` field                 | Must start with `@` and appear in the `prompt`                                                                           |
| I2V / Omni exclusion        | I2V fields and Omni fields cannot be used together                                                                       |

## Response

<ResponseField name="code" type="integer">
  Response status code, 200 on success
</ResponseField>

<ResponseField name="data" type="array">
  Response data array

  <Expandable title="Array Elements">
    <ResponseField name="status" type="string">
      Task status, `submitted` when initially submitted
    </ResponseField>

    <ResponseField name="task_id" type="string">
      Unique task identifier for querying task status and results
    </ResponseField>
  </Expandable>
</ResponseField>

## Request Examples

### Case 1: Text-to-Video (Minimal)

```json theme={null}
{
  "model": "skyreels-v4-fast",
  "prompt": "A serene forest at sunset with golden light filtering through the trees."
}
```

### Case 2: Text-to-Video (Full Parameters)

```json theme={null}
{
  "model": "skyreels-v4-std",
  "prompt": "A serene forest at sunset.",
  "duration": 5,
  "resolution": "720p",
  "aspect_ratio": "16:9",
  "prompt_optimizer": true
}
```

### Case 3: Image-to-Video - First Frame

```json theme={null}
{
  "model": "skyreels-v4-fast",
  "prompt": "Slowly pull the camera back to reveal the entire scene.",
  "first_frame_image": "https://example.com/start.png",
  "duration": 5
}
```

### Case 4: Image-to-Video - First/End Frame + Mid Keyframes

```json theme={null}
{
  "model": "skyreels-v4-std",
  "prompt": "The King summons a flying dragon. @image1 The dragon lowers. The King mounts and flies away.",
  "duration": 8,
  "resolution": "1080p",
  "first_frame_image": "https://example.com/k2v_0.png",
  "end_frame_image":   "https://example.com/k2v_2.png",
  "mid_frame_images": [
    { "tag": "@image1", "image_url": "https://example.com/k2v_1.png", "time_stamp": 3 }
  ]
}
```

### Case 5: Omni - Single Subject Reference

```json theme={null}
{
  "model": "skyreels-v4-fast",
  "prompt": "@Actor-1 walks through a neon-lit street at night.",
  "ref_images": [
    { "tag": "@Actor-1", "type": "image", "image_urls": ["https://example.com/actor.jpg"] }
  ]
}
```

### Case 6: Omni - Multi-Subject + Video Motion Reference

```json theme={null}
{
  "model": "skyreels-v4-fast",
  "prompt": "The man from @image_1 imitates the move on the left in @video_1. The woman from @image_2 imitates the right side.",
  "duration": 5,
  "ref_images": [
    { "tag": "@image_1", "type": "image", "image_urls": ["https://example.com/a.png"] },
    { "tag": "@image_2", "type": "image", "image_urls": ["https://example.com/b.png"] }
  ],
  "ref_videos": [
    { "tag": "@video_1", "type": "reference", "video_url": "https://example.com/motion.mp4" }
  ]
}
```

<Warning>
  This case uses `ref_videos.type=reference`, so **the requested `duration` will be overridden by the actual reference video length** (max 10 seconds). Even though `"duration": 5` is passed here, the final video length follows the reference video.
</Warning>

### Case 7: Omni - Grid Collage

```json theme={null}
{
  "model": "skyreels-v4-fast",
  "prompt": "Create a video showing how to make tomato and egg noodles based on @image1.",
  "ref_images": [
    { "tag": "@image1", "type": "grid", "image_urls": ["https://example.com/recipe_grid.png"] }
  ]
}
```

### Case 8: Omni - Video Extension (extend)

```json theme={null}
{
  "model": "skyreels-v4-fast",
  "prompt": "Video extended @video1, someone walks over and sits on the sofa.",
  "duration": 8,
  "ref_videos": [
    { "tag": "@video1", "type": "extend", "video_url": "https://example.com/source.mp4" }
  ]
}
```

### Case 9: Omni - Audio Sync (Voice-Driven)

```json theme={null}
{
  "model": "skyreels-v4-std",
  "prompt": "@Actor-1 speaks with a calm tone.",
  "ref_images": [
    {
      "tag": "@Actor-1",
      "type": "image",
      "image_urls": ["https://example.com/actor.jpg"],
      "audio_url":  "https://example.com/voice.mp3"
    }
  ]
}
```

<Note>
  **Query Task Results**

  Video generation is an async task that returns a `task_id` upon submission. Use the [Get Task Status](/en/api-reference/tasks/status) endpoint to query generation progress and results.
</Note>